Rainforests _____ and burned at such a speed that they will disappear from the earth in the near future.      [ ]

A. cut    

B. are cut  

C. are being cut  

D. have been cut

肌张力最大的收缩是（）

A.等长收缩

B.等张收缩

C.单收缩

D.不完全强直收缩

E.完全强直收缩